Joysticks have been known for several decades. Diagrammatically, they include a base, whereon is mounted a stick that can be moved in two directions x, y, defining a plane parallel to the base, and perpendicular to the axis zneutral defined by the stick when it is idle.
Means of detecting and measuring movement are provided in the base. As such, the movements applied to the stick by a user are detected, then generally converted into digital signals and transmitted by a wire or wirelessly to a device for processing data, such as a computer or a game console, so that the latter interprets these movements of the stick according to the software used.
Several techniques for detecting movement have been proposed. In particular, at the origin, four contacts were used, distributed in the shape of a cross according to the axes x and y. Today several techniques are used making it possible to define more precisely the position of the stick in relation to the base, for example based on potentiometers or Hall effect sensors, allowing for a detection of position without contact.
Joysticks include return means, tending to return the stick to a central position, or neutral position, when no effort is applied on the latter. This can in particular entail a helical spring acting on a part integral with the stick and mobile in the base. Different mounting alternatives of such a spring are shown for example in DE-10 2005 012 883, U.S. Pat. No. 5,891,462 or US-2007/026959.
Generally, the assembly of the spring, and therefore the parts whereon it presses against, are defined in such a way as to provide a sufficient resistance, but not too substantial, when the controller is displaced by the player, in particular in positions of maximum inclination, in relation to the axis of the stick in the neutral position (referred to as neutral axis, axis zn or axis zneutral). Another major aspect is that the spring must guarantee a quick and precise return in the neutral position, when the stick is released, without imprecision around the neutral position, or rebound effect around this position.
In order to satisfy these requirements, the spring must have a sufficiently high tension. However, the latter can cause problems of precision, and/or of feeling, in the manipulations carried out by the user, in particular when the latter wants to carry out movements of low amplitude, in the neighbourhood of the neutral position (also referred to as the idle position). Indeed, in this zone, the force applied by the spring is felt substantially, and is sometimes a hindrance in manipulating the stick. It is however not possible to reduce the force applied by the spring, as the latter is required in order to effectively return the stick to neutral position, when the stick has been highly inclined.
Moreover, the prior art joysticks encounter rebound problems around the neutral position of the stick when the user suddenly releases the stick, in particular because of the high tension of the spring. The rebound effect occurs, for example, if the stick is in the vicinity of the neutral position and the user releases the stick suddenly.